Electrolytic apparatus and methods for purification of aqueous solutions

ABSTRACT

Electropurification of contaminated aqueous media, such as ground water and wastewater from industrial manufacturing facilities like paper mills, food processing plants and textile mills, is readily purified, decolorized and sterilized by improved, more economic open configuration electrolysis cell designs, which may be divided or undivided, allowing connection as monopolar or bipolar cells. When coupled with very narrow capillary gap electrodes more economic operation particular when treating solutions of relatively low conductivity is assured. The novel cell design is also useful in the electrosynthesis of chemicals, such as hypochlorite bleaches and other oxygenated species.

FIELD OF THE INVENTION

The present invention relates generally to the purification of aqueoussolutions, and more specifically, to electrochemical methods and moreefficient and safer electrolytic apparatus for the destruction ofpollutants in drinking water, industrial waste waters and contaminatedground water.

BACKGROUND OF THE INVENTION

Wastewater can be a valuable resource in cities and towns wherepopulation is growing and water supplies are limited. In addition toeasing the strain on limited fresh water supplies, the reuse ofwastewater can improve the quality of streams and lakes by reducing theeffluent discharges they receive. Wastewater may be reclaimed and reusedfor crop and landscape irrigation, groundwater recharge, or recreationalpurposes.

The provision of water suitable for drinking is another essential oflife. The quality of naturally available water varies fromlocation-to-location, and frequently it is necessary to removemicroorganisms, such as bacteria, fungi, spores and other organisms likecrypto sporidium; salts, heavy metal ions, organics and combinations ofsuch contaminants.

Over the past several years, numerous primary, secondary and tertiaryprocesses have been employed for the decontamination of industrialwastewater, the purification of ground water and treatment of municipalwater supplies rendering them safer for drinking. They includeprincipally combinations of mechanical and biological processes, likecomminution, sedimentation, sludge digestion, activated sludgefiltration, biological oxidation, nitrification, and so on. Physical andchemical processes have also been widely used, such as flocculation andcoagulation with chemical additives, precipitation, filtration,treatment with chlorine, ozone, Fenton's reagent, reverse osmosis, UVsterilization, to name but a few.

Numerous electrochemical technologies have also been proposed for thedecontamination of industrial wastewater and ground water, includingtreatment of municipal water supplies for consumption. While growing inpopularity, the role of electrochemistry in water and effluent treatmentheretofore has been relatively small compared to some of the mechanical,biological and chemical processes previously mentioned. In someinstances, alternative technologies were found to be more economic interms of initial capital costs, and in the consumption of energy. Toooften, earlier electrochemical methods were not cost competitive, bothin initial capital costs and operating costs with more traditionalmethods like chlorination, ozonation, coagulation, and the like.

Earlier electrochemical processes required the introduction ofsupporting electrolytes as conductivity modifiers which adds tooperating costs, and can create further problems with the disposal ofby-products. Electrochemical processes in some instances have beenineffective in treating solutions by reducing concentrations ofcontaminants to levels permitted under government regulations.Heretofore, such electrochemical processes have often lacked sufficientreliability for consistently achieving substantially completemineralization of organic contaminants, as well as the ability to removesufficient color from industrial waste waters in compliance withgovernment regulations.

Notwithstanding the foregoing shortcomings associated with earlierelectrochemical technologies, electrochemistry is still viewed quitefavorably as a primary technology in the decontamination of aqueoussolutions. Accordingly, there is a need for more efficient and saferelectrochemical cell configurations and processes for more economictreatment of large volumes of industrial waste waters, effluent streamsand contaminated ground water, including the decontamination ofmunicipal water supplies making them suitable for drinking.

SUMMARY OF THE INVENTION

The present invention relates to improved means for electropurificationof aqueous solutions, particularly effluent streams comprising wastewaters polluted with a broad spectrum of chemical and biologicalcontaminants, including members from such representative groups asorganic and certain inorganic chemical compounds. Representativesusceptible inorganic pollutants include ammonia, hydrazine, sulfides,sulfites, nitrites, nitrates, phosphites, and so on. Included as organiccontaminants are organometallic compounds; dyes from textile mills;carbohydrates, fats and proteinaceous substances from food processingplants; effluent streams, such as black liquor from pulp and paper millscontaining lignins and other color bodies; general types of waterpollutants, including pathogenic microorganisms, i.e., bacteria, fungi,molds, spores, cysts, protozoa and other infectious agents like viruses;oxygendemanding wastes, and so on.

While it is impractical to specifically identify by name all possiblecontaminants which may be treated successfully according to the claimedmethods, it will be understood that language appearing in the claims,namely “contaminated aqueous electrolyte solution”, or variationsthereof is intended to encompass all susceptible pollutants whetherorganic, inorganic or biological.

The electropurification methods and apparatus for practicing thisinvention are particularly noteworthy in their ability to effectivelypurify virtually any aqueous solution comprising one or more organic,certain inorganic and biological contaminants present in concentrationsranging from as low as <1 ppm to as high as >300,000 ppm.

Only electricity is required to achieve the desired chemical change inthe composition of the contaminant(s), in most cases. The conductivityof tap water is sufficient for operation of the improved cell design.Hence, it is neither required, nor necessarily desirable to incorporateadditives into the contaminated aqueous solutions to modify theconductivity of the solution being treated to achieve the desireddecomposition of the pollutant/contaminant. Advantageously, in mostinstances solid by-products are not produced in the electropurificationreactions as to create costly disposal problems. The improvedelectrochemical processes of the invention are able to achieve completeor virtually complete color removal; complete mineralization of organiccontaminants and total destruction of biological pollutants even in thepresence of mixed contaminants, and at a cost which is competitive withtraditional non-electrochemical methods, such as chlorination, ozonationand coagulation, and thereby meet or exceed government regulations.

Accordingly, it is a principal object of the invention to provide anelectrolysis cell which comprises at least one anode and at least onecathode as electrodes positioned in an electrolyzer zone. The electrodesare preferably spaced sufficiently close as to provide an interelectrodegap capable of minimizing cell voltage and IR loss. Means are providedfor directly feeding the contaminated aqueous electrolyte solution tothe electrodes for distribution through the interelectrode gap(s). Meansare provided for regulating the residency time of the aqueouselectrolyte solution in the electrolyzer zone for modification ofcontaminants ether electrochemically by direct means and/or by chemicalmodification of contaminants to less hazardous substances duringresidency in the cell. Additional means are provided for collectingdecontaminated aqueous electrolyte solution descending from theelectrolyzer zone. It is also significant, the electrolysis cellaccording to the invention has an “configuration”.

In addition to the electrochemical cell of this invention, further meansare provided for practical and efficient operation, directly feedingcontaminated aqueous electrolyte solution to the cell by pump means orby gravity; pretreatment means for the contaminated aqueous electrolytesolutions, for example, means for aeration, pH adjustment, heating,filtering of larger particulates; as well as means for post-treatment,for example, pH adjustment and cooling, or chlorination to provideresidual kill for drinking water applications. In addition, theinvention contemplates in-line monitoring with sensors andmicroprocessors for automatic computer-assisted process control, such aspH sensors, UV and visible light, sensors for biological contaminants,temperature, etc.

It is still a further object of the invention to provide a system forpurification of aqueous solutions, which comprises:

(i) an electrolysis cell comprising at least one anode and at least onecathode as electrodes positioned in an electrolyzer zone. The electrodesare spaced sufficiently close to one another to provide aninterelectrode gap capable of minimizing cell voltage and IR loss. Alsoincluded is a conduit means for directly feeding a contaminated aqueouselectrolyte solution to the electrodes in the electrolyzer zone. Theelectrolysis cell is characterized by an open configuration.

(ii) A control valve means for regulating the flow of contaminatedaqueous-electrolyte solution to the electrodes directly via the conduitmeans of (i) above.

(iii) Means are included for pumping contaminated aqueous electrolytesolution through the conduit means, and then

(iv) rectifier means are included for providing a DC power supply to theelectrolysis cell.

The purification system may also include sensor means and computerizedmeans for receiving input from the sensor means and providing output forcontrolling at least one operating condition of the system selected fromthe group consisting of current density, flow rate of contaminatedaqueous solution to the electrolysis cell, temperature and pH of thecontaminated aqueous electrolyte solution. Optional components includeexhaust means for further handling of electrochemically produced gaseousby-products; means for pretreatment of the contaminated aqueouselectrolyte solution selected from the group consisting of filtration,pH adjustment and temperature adjustment.

As previously discussed, the electrochemical cells of this invention areespecially novel in their “open configuration.” As appearing in thespecification and claims, the expression “open configuration” orvariations thereof are defined as electrochemical cell designs adaptedfor controlled leakage or discharge of treated and decontaminatedaqueous electrolyte solution and gaseous or volatile by-products. Theabove definition is also intended to mean the elimination or exclusionof conventional closed electrochemical cells and tank type cell designsutilizing conventional indirect means for feeding electrolyte toelectrodes. Closed flow type electrochemical cells, for example, areoften fabricated from a plurality of machined and injection molded cellframes which are typically joined together under pressure into anon-leaking sealed stack with gaskets and O-rings to avoid any leakageof electrolyte from the cell. This type of sealed electrochemical cellis typically found in closed plate and frame type cells. Very closefitting tolerances for cell components are required in order to seal thecell and avoid leakage of electrolyte and gases to the atmosphere.Consequently, initial capital costs of such electrochemical cells,refurbishment costs, including replacement costs for damaged cell framesand gasketing from disassembly of closed plate and frame type cells arehigh.

Because the configuration of the electrochemical cells of this inventionis “open”, and not sealed, allowing for controlled leakage of aqueouselectrolyte solution and gaseous by-products, sealed cell designs,including gaskets, O-rings and other sealing devices are eliminated.Instead, cell component parts are retained together in close proximityby various mechanical means when needed, including, for instance,clamps, bolts, ties, straps, or fittings which interact by snappingtogether, and so on. As a result, with the novel open cell concept ofthis invention initial cell costs, renewal and maintenance costs areminimized.

In the open configuration cells of this invention, electrolyte is feddirectly to the electrodes in the electrolyzer zone from a feeder whichmay be positioned centrally relative to the face of the electrodes, forexample, where the contaminated solution engages with the electrodes byflowing through very narrow interelectrode gaps or spaces between theelectrodes. During this period the contaminants in the aqueous solutionare either directly converted at the electrodes to less hazardoussubstances and/or through the autogenous generation of chemical oxidantsor reductants, such as chlorine, bleach, i.e., hypochlorite; hydrogen,oxygen, or reactive oxygen species, like ozone, peroxide, e.g., hydrogenperoxide, hydroxy radicals, and so on, chemically modified to substancesof lesser toxicity, like carbon dioxide, sulfate, hydrogen, oxygen andnitrogen. In some instances, depending on the compositional make-up ofpollutants in the solution being treated, it may be desirable to addcertain salts like sodium chloride at low concentration to the solutionbefore treatment in the cell. For example, this could be used togenerate some active chlorine to provide a residual level of sterilantin the treated water. Likewise, oxygen or air may be introduced into thefeed stream to enhance peroxide generation.

Because electrolyte is fed directly to the electrode stack usually underpositive pressure, gases such as hydrogen and oxygen generated duringelectrolysis are less prone to accumulate over electrode surfaces byforming insulative blankets or pockets of bubbles. Gas blinding ofelectrodes produces greater internal resistance to the flow ofelectricity resulting in higher cell voltages and greater powerconsumption. However, with direct flow of electrolyte to the cell, thedynamic flow of solution in interelectrode gaps, according to thisinvention, minimizes gas blanketing, and therefore, minimizes cellvoltages.

The aqueous solution entering the cell by means of pumping or gravityfeed, cascades over and through available interelectrode gaps, and onexiting the electrolyzer zone of the cell through gravitational forces,descends downwardly into a reservoir, for post treatment, for example,or discharged, such as into a natural waterway. Any undissolved gasesgenerated by electrolysis, in contrast, are vented upwardly from thecell to the atmosphere or may be drawn into a fume collector or hood, ifnecessary, for collection or further processing.

While the direct feed “open configuration” electrochemical cells, asdescribed herein, preferably provide for the elimination of conventionalcell housings or tanks, as will be described in greater detail below,the expression “open configuration” as appearing in the specificationand claims, in addition to the foregoing definition, is also intended toinclude electrochemical cell designs wherein the directly fed electrodesare disposed in the interior region of an open tank or open cellhousing. A representative example of an open tank electrochemical cellis that disclosed by U.S. Pat. No. 4,179,347 (Krause et al) used in acontinuous system for disinfecting wastewater streams. The cell tank hasan open top, a bottom wall, sidewalls and spaced electrodes positionedin the tank interior. Instead of feeding the contaminated aqueoussolution directly to the electrodes positioned in the tank theelectrolyte, according to Krause et al, is initially fed to a first endof the tank where interior baffles generate currents in the wastewatercausing it to circulate upwardly and downwardly through and between theparallel electrodes. Hence, instead of delivering electrolyte directlyto the electrode stack where under pressure it is forced throughinterelectrode gaps between adjacent anodes and cathodes according tothe present invention, the electrolyte in the open tank cell of Krauseet al indirectly engages with the electrodes through a flooding effectby virtue of the positioning of the electrodes in the lower region ofthe tank where the aqueous solution resides. This passive, floodingeffect is insufficient to achieve the mass transport conditionsnecessary for efficient destruction particularly of contaminants whenpresent in low concentrations. Consequently, gaseous by-products of theelectrolysis reaction can and often do result in the development of ablanket of gas bubbles on electrode surfaces. This generates elevatedcell voltages and greater power consumption due to higher internalresistances.

Accordingly, for purposes of this invention the expression “openconfiguration” as appearing in the specification and claims is alsointended to include open tank type electrochemical cells wherein theelectrode stack is positioned in the interior of an open tank/housingand includes means for directly feeding contaminated aqueous solutionsto the electrodes. With direct feeding the housing does not serve as areservoir for the contaminated aqueous solution which otherwise wouldpassively engage the electrodes indirectly by a flooding effect.

For purposes of this invention, it is to be understood the expression“open configuration” is also intended to allow for safety devicespositioned adjacent to the electrochemical cells and purificationsystems, such as splash guards, shields and cages installed forminimizing the potential for injuries to operators. Hence, theconfinement of the electrolysis cells or an entire water purificationsystem of this invention inside a small room, for example, is alsointended to be within the meaning of “open configuration” as appearingin the specification and claims.

A further type of electrochemical cell design is disclosed by Beck et alin U.S. Pat. No. 4,048,047. The Beck et al cell design comprises abipolar stack of circular electrode plates separated by spacers toprovide interelectrode gaps ranging from 0.05 to 2.0 mm. Liquidelectrolyte is fed directly to the electrode plates through a pipelineinto a central opening in the electrode stack and then outwardly so itruns down the outside of the stack. However, the electrode stack isplaced in a conjoint closed housing with a covering hood to avoid lossof gaseous reactants, vapors or reaction products. Thus, the closedconfiguration of the Beck et al cell does not meet the criteria of an“open configuration” cell according to this invention.

While it has been pointed out the “open configuration” of the improved,highly economic electrochemical cell designs of this invention are basedon the elimination of traditional closed cell designs, including plateand frame type cells and conventional tank type cells, as well astraditional partially open tank type cell designs, whether batch orcontinuous, it is to be understood, the expression “open configuration”,as appearing in the specification and claims, also contemplateselectrochemical cells which may be modified with various inserts,barriers, partitions, baffles, and the like, in some instancespositioned adjacent to cell electrodes, or their peripheral edges. Suchmodifications can have the effect of altering electrolyte circulationand direction, and increase residency/retention time, and therefore,affect the residency time and rate of discharge of electrolyte from thecell. Notwithstanding, such modified electrochemical cells which aremade partially open fall within the intended meaning of “openconfiguration” when the electrodes per se remain substantiallyaccessible. Representative modified electrochemical cell designs withelectrodes which remain substantially accessible that are includedwithin the definition for “open configuration” as appearing in theclaims include modified, so called “Swiss roll cell” designs wherein,for example, the closed tubular containment for the electrodes, whichare superimposed onto one another and rolled up concentrically, isremoved, thereby forming an “open type Swiss roll cell”.

It is yet a further object of the invention to provide a more efficientelectrochemical cell design which can be used in effectively treating awide spectrum of both chemical and biological contaminants in aqueousmedia, but also of varying concentration (from less than a few ppm toseveral thousand ppm) which is both economically competitive in capitalcosts and power consumption to more conventional water purificationsystems. The electrochemical systems and methods of the invention havesuch significantly improved economics, as to be readily adaptable totreating via continuous processes, large volumes of industrial wastewaters from manufacturing facilities, such as chemical plants, textileplants, paper mills, food processing plants, and so on. Lower cellvoltages and higher current densities are achieved with the highlyeconomic, open configuration, especially when configured as monopolarelectrochemical cells equipped with electrodes having narrow capillaryinterelectrode gaps. Generally, the width of the gap between electrodesis sufficiently narrow to achieve conductivity without extra supportingelectrolytes or current carriers being added to the contaminated aqueoussolutions. Thus, the need for adding supporting electrolyte to thecontaminated aqueous electrolyte solution as supporting current carriercan be avoided. Because of the open configuration, as defined herein,the electrochemical cells of this invention can be readily configured toa monopolar design. This is especially advantageous since higher currentdensities would be desirable ih electrolyzing contaminated aqueoussolutions having relatively low conductivities while still alsomaintaining low cell voltages. Likewise, the improved electrochemicalcells of this invention may have a bipolar configuration, especially forlarge installations to minimize busbar and rectifier costs.

It is thus a further object of the invention to provide for improved,more economic and safer continuous, semi-continuous or batch methods forelectropurification of contaminated aqueous solutions by the steps of:

(i) providing an electrolysis cell comprising at least one anode and atleast one cathode as electrodes positioned in an electrolyzer zone. Theelectrodes are spaced sufficiently close to one another to provide aninterelectrode gap capable of minimizing cell voltage and IR loss. Meansare provided for direct feeding a contaminated aqueous solution to theelectrodes in the electrolyzer zone. Means are provided for regulatingthe residency time of the electrolyte solution in the electrolyzer zoneduring electrolysis for modification of the contaminants. Theelectrolysis cell is characterized by “open configuration” as previouslydescribed;

(ii) directly feeding into the electrolyzer zone of the electrolysiscell a contaminated aqueous electrolyte solution, and

(iii) imposing a voltage across the electrodes of the electrolysis cellto modify, and preferably destroy the contaminants in the aqueouselectrolyte solution.

It will be understood that generally the process will include the stepof recovering a purified electrolyte solution from the electrolysiscell. However, the invention contemplates direct delivery of purifiedaqueous solutions to a watershed, for example, or optionally to otherpost-treatment stations.

As previously mentioned, the methods is performed in an openconfiguration electrolysis cell which may be either monopolar or bipolarconfiguration.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the invention and its characterizingfeatures reference should now be made to the accompanying drawingswherein:

FIG. 1 is a side elevational view illustrating a first embodiment of adirect feed, open configuration, controlled leakage electrochemical cellof the invention wherein the electrodes are positioned above a watercollection vessel in a horizontal orientation;

FIG. 2 is a side elevational view of the electrochemical cell of FIG. 1except the electrodes are in a vertical orientation;

FIG. 3 is a side elevational view illustrating a second embodiment of adirect feed, open configuration, controlled leakage electrochemical cellof the invention wherein the electrodes are positioned in the interiorof an open cell housing;

FIG. 4 is an exploded view of the electrode cell stack of FIG. 1.

FIG. 5 is a side elevational view of an electrode stack of the inventionconnected in a monopolar configuration;

FIG. 6 is a side elevational view of an electrode stack of the inventionconnected in a bipolar configuration;

FIG. 7 is an elevational view of an electrode stack compartmentalizedwith a separator, and

FIG. 8 illustrates the results of electropurification of an aqueoussolution of phenol decontaminated according to the methods of theinvention, as performed in Example I

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning first to FIG. 1 there is illustrated an electrochemical cell 10for purification of contaminated aqueous solutions, as previouslydiscussed, represented by contaminated water 12 passing through inlet22. The contaminated water 12 is treated in the electrolyzer zone 14 ofcell 10 which is illustrated in a fully open configuration allowinggaseous by-products of the electrolysis reaction, such as oxygen andhydrogen 16 to be released to the atmosphere. It may be desirable insome instances to collect certain potentially hazardous gases generatedduring the electrolysis reaction to avoid discharging to the atmosphere.Chlorine, for example, may be generated at the anode during electrolysisof aqueous effluent streams containing brine or sea water. Such gasescan be recovered, for instance, by a vacuum powered hood device ofconventional design (not shown) positioned adjacent to electrochemicalcell 10.

The electrolyzer zone 14 includes an electrode stack 17 shown in ahorizontal orientation in FIGS. 1 and 4, and comprises at least onecathode 18 and at least one anode 20. Anodes 20, for example, may alsoserve as end plates 21 for holding an assembly of electrodes, spacers,and separators, whenever used, into an assembled electrode stack 17.Non-conductive electrode spacers 23 positioned between electrodesprovide the desired interelectrode gap or spacing between adjacentanodes and cathodes. While FIGS. 1 & 4 of the drawings may be shown withonly a central cathode with anodes on opposite sides of cathode 18, forexample, it is to be understood the electrode stacks may be formed fromseveral alternating anodes, spacers, cathodes, and so on, with boltingmeans 25 running through the stack and end plates for maintaining thecomponents in a structurally stable assembly.

The end plates, electrodes and spacers may have a generally rectangulargeometry. However, any number of possible alternative geometrical shapesand sizes are within the purview of the invention, including square,round or circular configurations, to name but a few. Contaminatedaqueous electrolyte solutions are fed directly to the electrodes inelectrolyzer zone 14 via supply line 22. Supply line 22 is showncentrally positioned relative to anode/end plate 21. The electrodes,which may be solid and planar, are preferably mesh/screen-typematerials. This enables the aqueous electrolyte solutions entering theelectrode stack to directly engage with the electrodes, and in so doingflow radially across the face of the individual electrode surfaceswithin the stack toward their peripheral edges. In addition, theentering solution usually flows axially, or normal to the longitudinalaxis of the plane of the electrodes, so the contaminated aqueoussolution simultaneously cascades over and through the electrode stack ina fountain-like effect to maximize contact with electrode surfaces inthe process. Purified water 24, free or virtually free of contaminantsexiting electrolyzer zone 14, can be collected in an open tank 26, orfunneled into a discharge line (not shown) for emptying into a naturalwatershed, etc.

It will be understood the direct feed of contaminated aqueous solutionsto the electrolyzer zone need not be centrally positioned relative tothe electrode stack, as illustrated in FIGS. 1-4. Alternative directfeed routes include inverting the point of feed, so that contaminatedaqueous solutions are fed from the bottom of the electrode stack, or atan oblique or obtuse angle to the planar surface of the electrodes. Inaddition, the direct feed entry point may also be axial with the edge ofthe planar surface of the electrodes wherein contaminated solution isdelivered to the peripheral edge of an electrode stack.

A convenient means for regulating the residency time of the contaminatedaqueous solution in electrolyzer zone 14 and for controlling leakage ofdecontaminated and purified water 24 therefrom can be through valve 28and/or pumping means of conventional design (not shown). The flow rateof contaminated water directly entering the electrode stack and exitingthe stack as decontaminated water can be regulated through manual orautomated flow control valve 28 of standard design. The flow rate(liters/minute)is adjusted, so it is sufficient to provide effectivedestruction of pollutants by the time the treated solution exits theelectrolyzer zone. Persons of ordinary skill in the art having thebenefit of this disclosure will also recognize the performance of theelectrochemical cells of this invention may be optimized by alternativemeans, such as increasing the path of the solution in the electrolyzerzone. The installation of baffles, for instance, can increase the dwelltime of the solution in the electrolyzer zone. Alternative means includeenlarging the surface area of the electrodes for reducing the residencytime in the electrolysis zone. In practice, electrochemists skilled inthe art will also recognize the performance of the cell can be increasedwith higher current densities.

Because of cell geometry, and the ability to conveniently use bothmonopolar and bipolar configurations, practically any electrode materialcan be employed, including metals in the form of flat sheet, mesh; foamor other materials, such as graphite, vitreous carbon, reticulatedvitreous carbon and particulate carbons. This also includes combinationsof electrode materials, such as bilayer structures comprising two metallayers separated by appropriate insulating or conductive materials, andso on.

Representative examples of useful anodes would include those generallyknown as, noble metal anodes, dimensionally stable anodes, carbon,vitreous carbon and graphite-containing anodes, doped diamond anodes,substoichiometric titanium oxide-containing anodes and leadoxide-containing anodes. More specific representative examples includeplatinized titanium noble metal anodes; anodes available under thetrademark DSA-O₂, and other anodes, such as high surface area typeanodes like felts, foams, screens, and the like available from TheElectrosynthesis Co, Inc., Lancaster, N.Y. Other anode materialscomprise ruthenium oxide on titanium, platinum/iridium on titanium,iridium oxide on titanium, silver oxide on silver metal, tin oxide ontitanium, nickel III oxide on nickel, gold, substoichiometric titaniumoxides, and particularly the so called Magneli phase titanium oxideshaving the formula TiO_(x) wherein x ranges from about 1.67 to about1.9. A preferred specie of substoichiometric titanium oxide is Ti₄O₇.Magneli phase titanium oxides and methods of manufacture are describedin U.S. Pat. No. 4,422,917 (Hayfield) which teachings areincorporated-by-reference herein. They are also commercially availableunder the trademark Ebonex®. Where electrocatalytic metal oxides, likePbO₂, RuO₂, IrO₂, SnO₂, Ag₂O, Ti₄O₇ and others are used as anodes,doping such oxides with various cations or anions has been found tofurther increase the electrocatalytic oxidation behavior, stability, orconductivity of the decontamination reactions of this invention. Theselection of appropriate anode materials is made by considering suchfactors as cost, stability of the anode material in the solutions beingtreated and its electrocatalytic properties for achieving highefficiencies.

Suitable cathode materials include metals, such as lead, silver, steel,nickel, copper, platinum, zinc, tin, etc., as well as carbon, graphite,Ebonex, various alloys, and so on. Gas diffusion electrodes are alsouseful in the methods of this invention. In this regard, they may beused as cathodes in converting oxygen or air to useful amounts ofperoxide, minimizing hydrogen evolution and/or for lowering cellvoltages. The electrode material, whether anode or cathode, may becoated with an electrocatalyst, either low or high surface area. Highersurface area electrodes, for example, expanded metal screens, metal orgraphite beads, carbon felts, or reticulated vitreous carbon areespecially useful in achieving higher efficiencies for destruction oftoxic or hazardous substances when present at low concentrations in theaqueous electrolyte.

Specific anode and cathode materials are selected on the basis of cost,stability and electrocatalytic properties. For example, persons ofordinary skill in the art of electrochemistry will recognize whichelectrode material to select when it is desired to convert chloride tochlorine; water to ozone, hydroxyl radicals or other reactive oxygenspecies; oxygen or air to hydrogen peroxide or hydroxyl radicals viaelectrochemically generated Fenton's reagent using for instance, aslowly dissolving iron-containing_metal anode; and catalytic reductionof nitrate to nitrogen or of_organohalogen compounds to halide ions andorganic moieties of lesser toxicity.

Of special importance in the selection of electrocatalytic anode andcathode materials occurs when treating aqueous solutions comprisingcomplex mixtures of pollutants wherein electrode materials may beselected for paired destruction of pollutants. For example, an aqueousstream contaminated with organics, microorganisms and nitrate pollutantsmay be treated simultaneously in the same electrochemical cell usingpaired destruction methods with a reactive oxygen species generatinganode, such as platinum on niobium or Ebonex for destruction ofmicroorganism and oxidation of organics. In addition, the same. cellcould also be equipped with a lead cathode for nitrate destruction.

As previously mentioned, non-conductive electrode spacers 23 provide thedesired interelectrode gap or spacing between adjacent anodes andcathodes. The thickness of spacers 23, which are non-conductive,insulative porous mesh screens fabricated from polymeric materials, suchas polyolefins, like polypropylene and polyethylene, determines thewidth of the interelectrode gap. Alternatively, it is permissible toemploy ionic polymer spacers which can effectively increase the ionicconductivity of the cell, so as to reduce cell voltage and operatingcosts further. Ion-exchange resins of suitable dimensions, like cationand anion exchange resin beads are held immobile within the gap betweenelectrodes.

For most applications, the interelectrode gap ranges from near zero gap,to avoid electrode shorting, to about 2 mm. More specifically, this verysmall capillary size gap is preferably less than a millimeter, rangingfrom 0.1 to <1.0 mm. The very small interelectrode gap makes possiblethe passage of current through relatively non-conductive media. This isthe case, for example, in water contaminated with organic compounds.Thus, with the present invention it is now possible to destroycontaminants in solution without adding any current carrying inorganicsalts to increase the ionic conductivity of the aqueous media.Furthermore, the very narrow interelectrode gap provides the importantadvantage of lower cell voltages which translates into reduced powerconsumption and lower operating costs. Hence, the combination of openconfiguration electrochemical cells and very narrow interelectrode gapsof this invention provide for both lower initial capital costs, as wellas lower operating costs. This achievement is especially important inlarge volume applications, as in the purification of drinking water, andwastewater, according to the claimed processes.

FIG. 2 represents a further embodiment of the electrochemical cells ofthis invention wherein the electrolyzer zone 30 is also in an openconfiguration. The electrolyte 32 is fed directly to the electrode stack34 which is in a vertical orientation. As a result, treated aqueoussolution 36 is shown exiting mainly from both the top and bottomperipheral edges of electrode stack 34. This may be altered furtherdepending on the use of baffles, for instance, in controlling residencytime for the solution being treated. Purified solution is collected invessel 38 below electrolyzer zone 30.

FIG. 3 represents still a: third embodiment of the invention wherein theelectrolyzer zone 40 comprises an electrode stack 42, as discussedabove, positioned in the interior of an open housing/tank 44. Housing 44is open at the top allowing gaseous by-products of the electrolysisreaction, like hydrogen and oxygen, for instance, to be readilydischarged into the atmosphere or collected through aid of anappropriate device, such as a hood (not shown). Aqueous contaminatedelectrolyte solution 46 is fed directly to electrode stack 42 positionedin open housing 44, unlike other tank cells wherein the electrodesreceive solution indirectly as a result of their immersion in thesolution delivered to the tank. Purified water 48 cascading downwardlyas a result of gravitational forces collects at the bottom of theinterior of housing 44, and is withdrawn.

An important advantage of the open configuration electrochemical cellsof this invention resides in their ability to be readily adaptable toeither a monopolar or bipolar configuration. In this regard, FIG. 5illustrates a monopolar open configuration electrochemical cell. In themonopolar cell of FIG. 5, anodes 52, 54 and 56 each require anelectrical connector as a current supply, in this case through a bus 58as a common “external” supply line similarly, cathodes 60 and 62 eachrequire an electrical connection shown through a common bus 64. It isalso characteristic of the monopolar cell design that both faces of eachelectrode are active, with the same polarity.

Because water purification for a municipality, in general, is a largevolume application, lowest possible cell voltages are essential in orderto minimize power consumption. The open configuration, monopolar celldesign of the present invention in combination with very narrowinterelectrode gaps offers not only the benefits of lower initialcapital costs, but also low operating costs, due to lower internalresistances, lower cell voltages and higher current densities. Thiscombination is especially desirable when treating contaminated aqueousmedia of relatively low conductivity without the addition of inorganicsalts as current carriers in accordance with certain embodiments of thisinvention, e.g., aqueous solutions contaminated with non-polar, organicsolvents.

The open configuration, monopolar, controlled leakage electrochemicalcells with very narrow interelectrode gaps of this invention areparticularly unique in light of the Beck et al cells of U.S. Pat. No.4,048,047. The closed configuration of the electrochemical cells of Becket al make it very difficult and costly to achieve a monopolarconnection with high current densities associated with externalelectrical contacts to each electrode. By contrast, with the openconfiguration of the electrochemical cells of this invention electricalconnections to individual electrodes are facilitated, irrespective ofwhether the cell is a monopolar or bipolar design. Thus, the closed,bipolar electrochemical cell configuration of Beck et al would not beeconomic and cost competitive with the improved electrochemical cells ofthe present invention, or with other non-electrochemical technologiesused in high volume water purification processes.

As previously indicated, the open configuration, controlled leakageelectrochemical cells of this invention having very narrow capillaryinterelectrode gaps are also readily adaptable to bipolar configuration.FIG. 6 illustrates open configuration bipolar cell 70, according to thepresent invention, requiring only two “external” electrical contacts 72and 74 through two end electrodes/end plates 76 and 78. Each of innerelectrodes 80, 82 and 84 of the bipolar cell has a different polarity onopposite sides. While the bipolar cell can be quite economic ineffectively utilizing the same current in each cell of the electrodestack, one important aspect of the invention relates to treatingsolutions by passing a current through relatively non-conductive mediausing very narrow interelectrode gaps. That is, the contaminated aqueoussolutions can have relatively low conductivities, about equivalent tothat of tap water. In order to efficiently treat such solutions it wouldbe desirable to operate at higher current densities. The monopolar cellconfigurations of the invention enable operating at desired low cellvoltages and high current density. While not specifically illustrated,it will be understood standard power supplies are utilized in theelectrolysis cells of the invention, including DC power supply, AC powersupply, pulsed power supply and battery power supply.

The invention also contemplates open configuration electrochemical cellswith distributor means for contaminated aqueous electrolyte solutions,such as a length of pipe 81 with multiple openings or pores, or a feedertube extending from the contaminated aqueous electrolyte feed inletthrough the depth of the electrode stack in the electrolyzer zone. Thiscan provide more uniform flow of solution to the electrode elements.Especially useful for stacks containing many electrode elements, theseporous tubes of metal or plastic material, of sufficient porosity,diameter and length, are applicable to monopolar, bipolar, and forexample, Swiss roll cells of open configuration. For deep cell stackswith electrode elements, each of larger surface area, more than oneporous feeder tube may be provided, manifolded together with the feedinlet conduit.

The open configuration, bipolar type, controlled leakage electrochemicalcells of the present invention can be most effectively used in thepurification of aqueous solutions possessing greater ionicconductivities than those previously discussed, allowing for economicaloperation at lower current densities. In each instance, the openconfiguration of the electrochemical cells of this invention facilitatestheir electrical connection, whether the cell is a monopolar or bipolardesign.

Most desirably, large volume applications like water purificationrequire low capital and operating costs in order to be economicallyattractive. These inventors found that capital costs are largely reducedby eliminating the need for precision machined components, gasketing,costly membranes and cell separators. Lower operating costs can beachieved through lower cell voltages from narrow interelectrode gaps andlower IR from elimination of cell membranes and separators, i.e.,undivided electrochemical cells. The smaller interelectrode gap,however, also makes possible the operation of the cells of thisinvention in an organic media, for example, containing lowconcentrations of supporting electrolyte, with a variety of electrode,insulator materials, and so on. Many of such applications would bereadily adaptable to the open cell configuration of this invention, butwith use of a cell divider forming anolyte and catholyte compartments,such as membranes or cell separators. Examples of useful processes forthe electrochemical cells of this invention would include mediatedreactions in electrochemical synthesis in which the objective of themembrane or separator would be to prevent reduction of anodicallyproduced species at the cathode, and/or oxidation of cathodicallyproduced species at the anode.

FIG. 7 is a representative example of an open configurationelectrochemical 90 having anode/end plates 92 and 94 with centralcathode 96 and cation exchange membranes 98 and 100 positioned betweenthe electrodes. Membranes 98 and 100 prevent mixing of the anolyte andcatholyte in the cell while the solution is allowed to flow throughopening 102 in the center of the membrane.

Those embodiments of the electrochemical cells employing a diaphragm orseparator are preferably equipped with ion-exchange membranes, althoughporous diaphragm type separators can be used. A broad range of inertmaterials are commercially available based on microporous thin films ofpolyethylene, polypropylene, polyvinylidene-difluoride, polyvinylchloride, polytetrafluoro-ethylene (PTFE), polymer-asbestos blends andso on, are useful as porous diaphragms or separators.

Useful cationic and anionic type permselective membranes arecommercially available from many manufacturers and suppliers, includingsuch companies as RAI Research Corp., Hauppauge, N.Y., under thetrademark Raipore; E.I. DuPont, Tokuyama Soda, Asahi Glass, and others.Generally, those membranes which are fluorinated are most preferredbecause of their overall stability. An especially useful class ofpermselective ion exchange membranes are the perfluorosulfonic acidmembranes, such as those available from E.I. DuPont under the Nafion®trademark. The present invention also contemplates membranes andelectrodes formed into solid polymer electrolyte composites. That is, atleast one of the electrodes, either anode or cathode or both anode andcathode, are bonded to the ion exchange membrane forming an integralcomponent.

In the purification of solutions the invention provides for thetreatment of low conductivity media. However, it may be necessary to addvery low concentrations of inert, soluble salts, such as alkali metalsalts, e.g. sodium or potassium sulfate, chloride, phosphate, to namebut a few. Stable quaternary ammonium salts may also be employed. Aspreviously mentioned, ion exchange resin beads of appropriate size canbe inserted in the spaces between the electrodes to increaseconductivity. This will provide further reductions in cell voltage andtotal operating costs.

Contaminated solutions entering the cell can range in temperature fromnear freezing to about boiling, and more specifically from about 40° toabout 90° C. Higher temperatures can be beneficial in lowering cellvoltages and increase rates of contaminant destruction. Such highertemperatures can be achieved, if needed, by preheating the incomingsolution, or through IR heating in the cell, especially when solutionconductivities are low, as for example in purification of drinkingwater. By suitably adjusting the cell voltage and residence time in thecell, beneficial temperatures in the above ranges are possible.

As a preferred embodiment of the invention, as an undivided cell, forthe purification of contaminated aqueous solutions a variety of usefulanode and cathode species can be generated during electrolysis which inturn aid in the chemical destruction of contaminants and thepurification of the aqueous solutions. They include such species asoxygen, ozone, hydrogen peroxide, hydroxyl radical, and other reactiveoxygen species. Less preferred species, although useful in the processinclude the generation of chlorine or hypochlorite (bleach) through theelectrolysis of brine or sea water. While not wishing to be held to anyspecific mechanism of action for the success of the processes in thedecontamination, decolorization and sterilization of aqueous solutionscontaminated with toxic organics and microorganisms, several processes,including those previously mentioned, may be occurring simultaneously.They include, but are not limited to the direct oxidation ofcontaminants at the anode; destruction of contaminants by directreduction at the cathode; oxygenation of the feed stream by microbubbles of oxygen produced at the anode; degasification of volatiles inthe feed stream by oxygen and hydrogen micro bubbles; IR heating in thecell; aeration of the water stream exiting the open cell, and so on.

A broad range of compounds, microorganisms and other hazardoussubstances as previously discussed are successfully destroyed in theopen cell configuration of the invention employing the processes asdescribed herein. Representative examples include aliphatic alcohols,phenols, nitrated or halogenated aromatic compounds, and so on. Colorreduction or complete elimination of color can also be achieved, alongwith disinfection, including the destruction of viruses.

The following specific examples demonstrate the various embodiments ofthe invention, however, it is to be understood they are for illustrativepurposes only and do not purport to be wholly definitive as toconditions and scope.

EXAMPLE I

A monopolar electrochemical cell having an open configuration was set upwith an electrode stack comprising 316 stainless steel end plates eachwith a diameter of 12.065 centimeters and a thickness of 0.95centimeters. The end plates were connected as cathodes. A centralcathode was also assembled into the stack and consisted of 316 stainlesssteel mesh with 7.8×7.8 openings/linear centimeter, 0.046 centimeterwire diameter, 0.081 centimeter opening width and 41 percent open area.The anodes consisted of two platinum clad niobium electrodesmanufactured by Blake Vincent Metals Corp. of Rhode Island. The anodeswhich were clad on both sides of the niobium substrate had a thicknessof 635 micrometers, were expanded into a mesh with a thickness of about0.051 centimeters, with 0.159 centimeter diamond shaped interstices. Thespacers positioned between adjacent electrodes were fabricated frompolypropylene mesh with 8.27×8.27 openings/linear centimeter, 0.0398centimeter thread diameter, 0.084 centimeter opening and a 46 percentopen area was supplied by McMaster-Carr of Cleveland, Ohio. The gapbetween the electrodes was approximately 0.04 centimeters, determined bythe thickness of the polypropylene mesh. A schematic of theelectrochemical cell corresponds to FIG. 1 of the drawings, except ahood was omitted. Recirculation of the aqueous solution between theglass collection tank and the cell was effected by means of an AC-3C-MDMarch centrifugal pump at a flow rate of about 1 liter/minute. ASorensen DCR 60-45B power supply was used to generate the necessaryvoltage drop across the cell.

A test solution was prepared containing 1 g of phenol in 1 liter of tapwater. The solution was recirculated through the cell while a constantcurrent of 25 amps was passed. The solution which was initially clearturned red after about 2-3 minutes into the treatment process, possiblyindicating the presence of quinone-type intermediates. The initial cellvoltage of 35 V decreased rapidly to 8-9 V, and the temperature of thesolution stabilized at about 56-58° C. Samples taken were analyzedperiodically for total organic carbon (TOC). The results, which areshown in FIG. 8, appear to suggest the decrease in TOC is from thephenol probably undergoing complete oxidation to carbon dioxide which isthen eliminated as gas from the solution.

EXAMPLE II

In order to demonstrate color reduction in a textile effluent 1 liter ofsolution was prepared with tap water containing 0.1 g of the textile dyeRemazol™ Black B (Hoechst Celanese), 0.1 g of the surfactant Tergitol™15-S-5 (Union Carbide) and 1 g of NaCl.

The composition of the test solution was similar to that of typicaleffluents produced in textile dyeing processes where even very lowconcentrations of Remazol Black impart very strong coloration tosolutions. Remazol Black is a particularly difficult to treat textiledye. Heretofore, other methods used to treat Remazol Black, such as byozonation or with hypochlorite bleach have failed to producesatisfactory color reduction.

The above solution containing Remazol Black was electrolyzed in themonopolar cell set up of Example I above, at a constant current of 25amps. The cell voltage was about 25 V, and the temperature of thesolution reached 52° C. The initial color of the solution was dark blue.After 10 minutes of electrolysis the color of the solution turned topink, and after 30 minutes the solution was virtually colorless.

EXAMPLE III

A further experiment was conducted in order to demonstrate thedecontamination of ground water. Humic acids are typical contaminants ofground water, produced by the decomposition of vegetable matter. Watercontaining humic acids is strongly colored even at low concentrations,and the elimination of the color can be difficult.

A dark brown solution in tap water was prepared containing 30 ppm of thesodium salt of humic acid (Aldrich) without any additives to increasethe electrical conductivity of the solution. The solution wasrecirculated through a monopolar electrochemical cell similar to thatused in Example I, but equipped with only one anode and two cathodes. Aconstant current of 10 amps was passed for 2.5 hours. The cell voltagewas 24-25 volts, and the temperature reached 58° C. At the end of theexperiment the solution was completely clear, demonstrating theeffective destruction of humic acid.

EXAMPLE IV

A further experiment was conducted to demonstrate the effectiveness ofthe electrolysis cells and methods of this invention in thesterilization and chemical oxygen demand (COD) reduction in effluentsfrom food processing plants.

250 ml of wastewater from a Mexican malt manufacturing company wastreated using a monopolar, open electrochemical cell similar to thatemployed in Example I, except the total anode area of 6 cm². Theobjectives were to reduce the COD, partial or total reduction of thecolor, elimination of microorganisms and odor.

A current of 1 amp was passed for 150 minutes; the initial cell voltageof 22 V dropped to 17.5 V, and the temperature of the solution reached44° C.

The results are shown in the following Table:

TABLE Initial Final COD 1700 ppm 27 ppm Color Yellow-Orange ClearMicroorganisms Active Sterilized Odor Yes No

EXAMPLE V

A further experiment was conducted to demonstrate the effectiveness ofthe electrolysis cells and methods of this invention in the removal ofcolor in a single-pass configuration.

A dark purple solution containing methyl violet dye in tap water at aconcentration of 15 ppm was circulated through a monopolar, openelectrochemical cell similar to that employed in Example 1, insingle-pass mode, at a flow rate of 250 ml/minute. The objective was toachieve total reduction of the color.

A current of 25 amp was passed; the cell voltage was 25 V, and thetemperature of the solution reached 65° C.

After a single pass through the cell a clear solution was obtained.

EXAMPLE VI

An experiment can be conducted to demonstrate the utility of the openconfiguration electrochemical cell in the electrosynthesis of chemicals,in this instance sodium hypochlorite.

The electrochemical cell of Example I is modified by replacing theanodes with catalytic chlorine evolving anodes, such as DSA® anodesmanufactured by Eltech Systems. A solution of brine containing 10 g ofsodium chloride per liter is introduced into the electrolyzer zonewherein chlorine is generated at the anode and sodium hydroxide isproduced at the cathode. The chlorine and caustic soda are allowed toreact in the cell to produce a dilute aqueous solution of sodiumhypochlorite bleach.

While the invention has been described in conjunction with variousembodiments, they are illustrative only. Accordingly, many alternatives,modifications and variations will be apparent to persons skilled in theart in light of the foregoing going detailed description, and it istherefore intended to embrace all such alternatives and variations as tofall within the spirit and broad scope of the appended claims.

We claim:
 1. An open configuration electrolysis cell, which comprises atleast one anode and at least one cathode as electrodes positioned in anelectrolyzer zone, said electrodes spaced from one another, saidelectrolysis cell excluding a cell housing intended for retaining anaqueous electrolyte solution in said electrolyzer zone.
 2. Theelectrolysis cell of claim 1 wherein said open configuration ischaracterized by controlled leakage.
 3. The electrolysis cell of claim 1wherein said electrodes are connected in a monopolar configuration. 4.The electrolysis cell of claim 1 wherein said electrodes are connectedin a bipolar configuration.
 5. The electrolysis cell of claim 1 which isa Swiss roll cell.
 6. The electrolysis cell of claim 1 including meansfor continuously collecting modified aqueous electrolyte solutiondescending from said electrolyzer zone.
 7. The electrolysis cell ofclaim 1 including means for regulating residency time comprising pumpingmeans, control valve means or a combination of pumping means and controlvalve means.
 8. The electrolysis cell of claim 1, including means foruniform distribution of contaminated aqueous electrolyte solution overthe electrodes.
 9. The electrolysis cell of claim 1 wherein saidelectrodes are substantially parallel and positioned in a generallyhorizontal plane.
 10. The electrolysis cell of claim 1 wherein saidelectrodes are substantially parallel and positioned in a generallyvertical plane.
 11. The electrolysis cell of claim 1 wherein said anodesare electrocatalytic for producing reactive oxygen species.
 12. Theelectrolysis cell of claim 11 wherein the electrocatalytic anodescomprise a member selected from the group consisting of noble metal, tinoxide, lead dioxide, substoichiometric titanium oxide and doped diamond.13. The electrolysis cell of claim 1 wherein said cathodes areelectrocatalytic for nitrate destruction.
 14. The electrolysis cell ofclaim 1 wherein said cathodes are gas diffusion cathodes suitable forreduction of oxygen to water or peroxide.
 15. The electrolysis cell ofclaim 1 which is an undivided electrochemical cell.
 16. The electrolysiscell of claim 1 including a cell divider forming anolyte and catholytecompartments.
 17. The electrolysis cell of claim 16 wherein said celldivider is a diaphragm, microporous separator, ion exchange membrane ora bipolar membrane.
 18. The electrolysis cell of claim 1 including ionexchange particulates, beads or solid polymer electrolyte positioned insaid interelectrode gaps.
 19. The electrolysis cell of claim 1 whereinthe inter-electrode gap is from nearly about zero to about 2.0 mm. 20.The electrolysis cell of claim 19 including electrically insulatingspacers positioned between electrodes wherein the thickness of saidspacers determines the width of the interelectrode gap.
 21. Theelectrolysis cell of claim 1 including at least one sensor selected fromthe group consisting of pH, UV light, visible light conductivity,hydrogen and chlorine.
 22. The electrolysis cell of claim 1, includingat least one power supply selected from the group consisting of a DCpower supply, AC power supply, pulsed power supply and battery powersupply.
 23. The electrolysis cell of claim 1 wherein at least one ofsaid electrodes comprises a high surface area.
 24. The electrochemicalcell of claim 1 which is also a hypochlorite generator.
 25. A system forpurification of aqueous solutions, which comprises: (i) an openconfiguration electrolysis cell comprising at least one anode and atleast one cathode as electrodes positioned in an electrolyzer zone, saidelectrodes spaced from one another, said electrolysis cell excluding acell housing intended for retaining an aqueous electrolyte solution insaid electrolyzer zone; (ii) control valve means for regulating the flowof contaminated aqueous electrolyte solution to said electrodes; (iii)means for pumping contaminated aqueous electrolyte solution to saidelectrodes, and (iv) rectifier means for providing a DC power supply tosaid electrolysis cell.
 26. The purification system of claim 25,including sensor means and computerized means for receiving input fromsaid sensors and providing output for controlling at least one operatingcondition in said system selected from the group consisting of currentdensity, flow rate of contaminated aqueous solution to said electrolysiscell, temperature and pH of the contaminated aqueous electrolytesolution.
 27. The purification system of claim 26, including exhaustmeans for further handling of electrochemically produced gaseousby-products.
 28. The purification system of claim 24, including meansfor pretreatment of said contaminated aqueous electrolyte solutionselected from the group consisting of filtration, pH adjustment andtemperature adjustment.
 29. A method for electropurification of acontaminated aqueous solution, which comprises the steps of: (i)providing an open configuration electrolysis cell comprising at leastone anode and at least one cathode as electrodes positioned in anelectrolyzer zone, said electrodes spaced from one another, saidelectrolysis cell excluding a cell housing intended for retaining anaqueous electrolyte solution in said electrolyzer zone; (ii) introducinginto the electrolysis cell of (i) a contaminated aqueous electrolytesolution, and (iii) imposing a voltage across the electrodes of saidelectrolysis cell to electrolyze the contaminated aqueous solution tomodify the contaminants therein.
 30. The electropurification method ofclaim 29 including the step of collecting the modified electrolytesolution from said electrolysis cell.
 31. The electropurification methodof claim 29 wherein the aqueous electrolyte solution comprisescontaminants selected from the group consisting of organic compounds,inorganic compounds, microorganisms, viruses and mixtures thereof. 32.The electropurification method of claim 31 wherein the aqueouselectrolyte solution introduced into said electrochemical cell comprisescontaminants selected from the group consisting of bacteria, spores,cysts, protozoa, fungi and mixtures thereof.
 33. The electropurificationmethod of claim 29 wherein the aqueous electrolyte solution introducedinto the electrolysis cell is a textile effluent comprising dyes orother color producing contaminants, and the modified aqueous electrolytesolution recovered from said electrolysis cell is substantiallycolor-free.
 34. The electropurification method of claim 29 wherein thecontaminated aqueous electrolyte solution is electrolyzed at atemperature ranging from about the freezing point of the contaminatedsolution to above about ambient temperature.
 35. The electropurificationmethod of claim 29 wherein the contaminated aqueous electrolyte solutionis electrolyzed at a temperature ranging from about 40° to about 90° C.36. The electropurification method of claim 29 wherein said electrodesof said electrolysis cell are connected in a monopolar configuration.37. The electropurification method of claim 29 wherein said electrodesof said electrolysis cell are connected in a bipolar configuration. 38.The electropurification method of claim 29 conducted in a batch mode.39. The electropurification method of claim 29 conducted in a continuousor semi-continuous mode.
 40. The electropurification method of claim 29wherein said electrochemical cell of step (i) is a component part of aportable battery powered water purifier.
 41. The electropurificationmethod of claim 29 including the autogenous generation of at least oneoxidizing chemical in the contaminated aqueous electrolyte solution. 42.The electropurification method of claim 29 including the generation of achemical agent in the contaminated aqueous electrolyte solution selectedfrom the group consisting of hydrogen peroxide, ozone, oxygen, hydroxylradical, hypochlorite ion, chlorine and mixtures thereof.
 43. Theelectropurification method of claim 29 wherein electrolysis is conductedwithout the introduction of a current carrier to the aqueous electrolytesolution.
 44. The electropurification method of claim 29 whereinelectrolysis is conducted with the introduction of a current carrier tothe aqueous electrolyte solution in an amount sufficient to enhance thedestruction of contaminants.
 45. The electropurification method of claim44 wherein the current carrier is an alkali metal or a quaternaryammonium salt selected from the group consisting of chloride, phosphateand sulfate.
 46. The electropurification method of claim 29 includingthe step of adding sufficient salt to the contaminated aqueouselectrolyte solution to provide an active halogen residue in thepurified water.
 47. The electropurification method of claim 29 whereinthe contaminated aqueous electrolyte solution is sufficiently modifiedto produce potable water.